docs: def _do_post_text(tx):
      """
      Try to find out what the variables mean:
  
      tx         A structure containing more informations about paragraph ???
  
      leading    Height of lines
      ff         1/8 of the font size
      y0         The "baseline" postion ???
      y          1/8 below the baseline
      """
  
      xs = tx.XtraState
      leading = xs.style.leading
      autoLeading = xs.autoLeading
      f = xs.f
      if autoLeading == 'max':
          # leading = max(leading, f.fontSize)
          leading = max(leading, LEADING_FACTOR * f.fontSize)
      elif autoLeading == 'min':
          leading = LEADING_FACTOR * f.fontSize
      ff = 0.125 * f.fontSize
      y0 = xs.cur_y
      y = y0 - ff
  
      # Background
      for x1, x2, c, fs in xs.backgrounds:
          inlineFF = fs * 0.125
          gap = inlineFF * 1.25
          tx._canvas.setFillColor(c)
          tx._canvas.rect(x1, y - gap, x2 - x1, fs + 1, fill=1, stroke=0)
      xs.backgrounds = []
      xs.background = 0
      xs.backgroundColor = None
      xs.backgroundFontSize = None
  
      # Underline
      yUnderline = y0 - 1.5 * ff
      tx._canvas.setLineWidth(ff * 0.75)
      csc = None
      for x1, x2, c in xs.underlines:
          if c != csc:
              tx._canvas.setStrokeColor(c)
              csc = c
          tx._canvas.line(x1, yUnderline, x2, yUnderline)
      xs.underlines = []
      xs.underline = 0
      xs.underlineColor = None
  
      # Strike
      for x1, x2, c, fs in xs.strikes:
          inlineFF = fs * 0.125
          ys = y0 + 2 * inlineFF
          if c != csc:
              tx._canvas.setStrokeColor(c)
              csc = c
          tx._canvas.setLineWidth(inlineFF * 0.75)
          tx._canvas.line(x1, ys, x2, ys)
      xs.strikes = []
      xs.strike = 0
      xs.strikeColor = None
  
      yl = y + leading
      for x1, x2, link, c in xs.links:
          # No automatic underlining for links, never!
          _doLink(tx, link, (x1, y, x2, yl))
      xs.links = []
      xs.link = None
      xs.linkColor = None
      xs.cur_y -= leading